1. Field of the Invention
This invention relates to the application of herbicides and more particularly to an apparatus carried by a farm machine and adapted to wipingly apply liquid herbicide on undesired vegetation in cultivated fields.
2. Description of the Prior Art
The prior art is replete with mechanisms which are carried by wheeled vehicles for the purpose of wipingly or sprayingly applying insecticides on crop plants growing in cultivated fields.
U.S. Pat. No. 1,109,060, issued on Sept. 1, 1914, to W. F. Griffin discloses a vehicle including mechanisms for applying insecticide to crop plants. The vehicle has a support frame extending rearwardly therefrom to support a transverse pipe which extends horizontally across the back of the vehicle. A liquid reservoir tank is disposed above the pipe and is connected thereto to supply liquid to the center of the pipe. The pipe is provided with three suitable flow control valves, one depending from the mid point of the pipe and the other two depending from the opposite ends thereof. Each of the valves are coupled to the mid points of a different one of three separate horizontally disposed perforated pipes each of which supports a depending fabric apron of sheet-like configuration. Liquid flows from the reservoir tank to the transverse pipe and through the control valves to the perforated pipes. The liquid emerging from the perforated pipes will saturate the aprons which wipingly apply the liquid on the crop plants as the vehicle is moved through the field.
U.S. Pat. No. 2,223,809, issued on Dec. 3, 1940, to H. M. B. Rucker discloses another vehicle having a mechanism thereon for wipingly applying insecticide on crop plants. The vehicle includes a transverse rockshaft supported atop standards carried on the rear of the vehicle. A pair of coupling blocks are carried adjacent the opposite ends of the rockshaft and are longitudinally adjustable thereon. Each of these coupling blocks has a vertically adjustable rod carried therein with an insecticide applying device mounted on the lower end of the vertical rod. The insecticide applying device includes a longitudinally extending horizontal conduit for receiving liquid insecticide from a tank carried on the vehicle and delivering it to horizontally disposed cross pipes at the opposite ends of the conduit. Each of the cross pipes is provided with a pair of mop-like depending wiper elements which absorb the insecticide and wipingly apply it to the crop plants. The rockshaft is coupled to one of the vehicle's wheels in a manner which results in the applicator device swinging in an arc as the vehicle moves through the field.
U.S. Pat. No. 1,518,305, issued on Dec. 9, 1924, to H. V. Carmans discloses a wheeled vehicle including plural brush assemblies A, B, and C and apparatus for spraying liquid insecticide through the brushes onto the crop plants. Brush assembly A is at the front of the vehicle and is reciprocally moved in a vertical plane to brush the crop plants and spray them with insecticide. Brush assembly B is fixed at the back of the machine at a height which brushes the tops of the crop plants and again, liquid herbicide is sprayed through the brush assembly B onto the crop plants. Brush assemblies C are disposed at opposite sides of the machine and are reciprocally movable in a path longitudinal of the machine to sweep Weevils dislodged by brushes A toward the center of the machine into the spray path of brushes B.
The purposes of each of these above discussed prior art structures is to apply liquid insecticide directly on and in the vicinity of crop plants growing in a cultivated field. The application of liquid herbicide on the other hand poses entirely different problems in that in order to be effective, the herbicide must be applied to undesired vegetation while avoiding contact with the crop plants. In other words, selective application of a liquid herbicide is critical, whereas, application selectivity of liquid insecticide is of little or no consequence. For this basic reason, spray techniques per se, such as that taught by the Carmans patent is unsuited in that no selective application is possible with a spray. The prior art trailing wiping elements, such as the fabric aprons of the Griffin patent and the mop-like elements of the Rucker patent, are also unsuited for selective application of herbicide, in that they can be readily deflected, or otherwise moved, out of their intended path of movement into an unintended path. If either of these prior art structures were employed to apply herbicide on noxious weeds, due to their non-rigid character, they could be deflected by weeds, blown by winds, or otherwise moved into contact with crop plant and this would, of course, destroy the crop plants.
In addition, liquid leakage such as dripping, from any of the plural wiper elements is of no particular consequence in devices that are employed for the application of insecticides. However, leakage must be prevented in herbicide applicator devices to prevent destruction of the crop plants.
In addition to conventional herbicides which burn vegetation, a comparatively new type of herbicide has been developed which is sometimes referred as a systemic herbicide. A systemic herbicide is one which will be absorbed by the vegetation to which it is applied and will permeate the vegetation to kill the root systems without effecting the soil in any way. Both conventional and systemic herbicides may be applied by the well known spray technique when complete destruction of all plant life in the sprayed area is desired. However, selective herbicidal tasks, such as weeding operations require that the herbicide be selectively applied only to the vegetation that is to be destroyed.
As is well known, weeds will normally outgrow crop plants particularly in the early stages of crop growth, and a particular prior art herbicide applicator mechanism has been suggested which takes advantage of this differential in growth rates. This particular prior art device is fully disclosed in U.S. Pat. No. 4,019,278, as including a pair of spaced parallel rigid tubes supportingly carried on a tractor so as to extend transversely thereof. The tubes are in a closed loop configuration and are connected to a source of liquid herbicide with a flow control device interposed therebetween. The liquid herbicide flows into the tubes and coates the exterior surfaces thereof and by movement of the tractor through the cultivated field, the herbicide is wiped on the tops of weeds which have outgrown the crop plants. The two tubes are suggested as being configured in either of two embodiments, one being a porous plastic and the other being a wicking element in the form of a sleeve-like member which circumscribes a drilled tube. The spaced tubes are attached to a supporting structure provided on the tractor, which can be raised and lowered hydraulically.
This prior art device, and others similar thereto, have not achieved any appreciable commercial success for several reasons. The first of these reasons is a problem of liquid distribution. The portion of tubular wicking elements nearest the source of the herbicide becomes overly wetted while those portions remote from the source are comparatively dry. The excessively wet portions of the wicking element can become so wet that they drip, and uncontrolled dripping can kill the desired crop plants. The relatively dry portions on the other hand become so dry that insufficient amounts of the herbicide are applied so that many weeds are not destroyed. This inherent problem is further complicated when the mechanized vehicle is operating on a slope, in that one end of the closed loop tubular wicking element will become overly wetted while the other becomes dry.
A second problem, or shortcoming, with the above described prior art structure is that it makes no provisions for wipingly applying herbicide to undesired vegetation growing in the furrows, or spaces between the crop plants.
A further problem, or shortcoming associated with this prior art device is that its wiper elements are rigid non-formable structures which lie in a substantially horizontal plane and the only adjustment, which is provided by the tractor, is that the height of the horizontal plane of the wiper elements can be raised and lowered to just clear the tops of the crop plants. This rigid non-formability of the wiper elements permits the liquid herbicide to be wipingly applied only on the noxious weeds which are taller than the crop plants, and this, in conjunction with the above discussed second problem, or shortcoming, results in the application of herbicide only on a relatively small percentage of the weeds growing in a cultivated field.
Another prior art device has been devised for applying liquid herbicide on noxious weeds growing in the furrows, or spaces between crop plants. This device includes a wicking element carried on the front of a farm machine with the wicking element being positioned at the rear opening of forwardly diverging plates which deflect the undesired vegetation into contact with the wicking element. This device is positioned so that it lies in the furrow between crop plants and will wipingly apply the herbicide on the inwardly deflected undesired vegetation in the furrow. Such a device is limited as to its width in that the diverging plates cannot be allowed to come to close to the crop plants lest they strikingly damage the crop plants or deflect them into contact with the wicking element.
Therefore, a need exists for a new and improved liquid herbicide applicator mechanism which overcomes some of the problems and shortcomings of the prior art.